High frequency electrodeless fluorescent lamp assembly



y 21, 7 J. M. ANDERSON 3,521,120

HIGH FREQUENCY ELECTRODELESS FLUORESCENT LAMP ASSEMBLY Filed March 20, 1968 23 l5 Inventor":

' I do nM/Jn enson,

' 1's Attorney.

United States Patent HIGH FREQUENCY ELECTRODELESS FLUORESCENT LAMP ASSEMBLY John M. Anderson, Scotia, N.Y., assignor to General Electric Company, a corporation of New York Filed Mar. 20, 1968, Ser. No. 714,506 Int. Cl. Htllj 11 /02, 65/04; H05]: 41 /24 U.S. Cl. 315-57 9 Claims ABSTRACT OF THE DISCLOSURE A fluorescent lamp adapted to fit into a standard incandescent lamp fixture includes an integral member having a contact base, a self-contained solid-state radiofrequency oscillator and a cylindrical, rod-shaped ferrite core with coupling means between core and oscillator. A removable lamp envelope includes an annular, hermeti- Cally-sealed bulb adapted to rest in place surrounding the ferrite core and to be activated thereby. Bulb contains an ionizable medium and a luminescent phosphor. Means are provided to secure the bulb upon the core in fixed relationship during operation.

The present invention relates to fluorescent lamps adapted to be substituted for conventional incandescent lamps. More particularly, the present invention is related to such lamps as are operated without the use of electrodes within the discharge envelope.

In the illuminating arts, the incandescent lamp is a 0 very high quantity item, utilized primarily in household and other residential uses. This lamp generally includes an incandescent filament within a predetermined nonoxidizing atmosphere and contained within a tear-shaped envelope which is mounted, for example, within a screwtype base which is screwed into a permanent fixture or into a moveable socket or similar adaptation thereof.

Despite the overwhelming preponderance of the use of incandescent lamps in residential uses, primarily low power and low voltage uses, such lamps are subject to great disadvantages. Of these disadvantages, the low eificiency is perhaps one of the greatest. This efficiency is as low as approximately 15 lumens per watt or of the order of 2 to 3 percent total efliciency, since the greatest proportion of the energy irradiated by the incandescent filament is in the form of invisible infrared radiation which is dissipated as heat. Another great disadvantage of incandescent lamps is that the lifetime of these lamps is exceedingly short and is very unpredictable, due to the great fragility of the suspension of the incandescible filament within the lamp envelope upon suitable support means. Any sudden mechanical or thermal shock is likely to fracture the filament or cause it to be dislodged from the lead-in electrodes.

Accordingly, it is a primary object of the present invention to provide a fluorescent type lamp suitable for economic substitution in place of the conventional incandescent type lamp.

Yet another object of the present invention is to provide low power, low voltage fluorescent lamps for household and similar uses which do not require the use of a ballast transformer.

Still another object of the present invention is to provide a fluorescent lamp assembly for household and similar uses which contains a permanent voltage supply and a replaceable fluorescent envelope.

Yet another object of the present invention is to provide a high-eificiency fluorescent lamp suitable for household and similar applications.

Briefly stated, in accord with the present invention, I provide a fluorescent lamp adapted to be substituted for 3,521,120 Patented July 21, 1970 ice a conventional incandescent lamp and fitted into a conventional incandescent lamp socket. Lamps constructed in accord with the present invention include a permanent support member including a suitable base contact mernher, a solid-state voltage-generating member, a ferrite core for coupling operating power to the light-emitting member of the apparatus and means for attaching a light-emitting member thereto. These lamps also contain a replaceable fluorescent light-emitting member in the shape of an annular light-transmissive envelope containing a fluorescent phosphor and adapted to be removably placed over the ferrite core and temporarily fixed in immoble relation thereto for operation by the voltage induced therein by the ferrite core. Upon failure, this light emissive fluorescent assembly may be removed and replaced, without replacing the support member and the ferrite core.

The novel features believed characteristic of the present invention are set forth in the appended claims. The invention itself, together with further objects and advantages thereof, may be best understood with reference to the following detailed description, taken in connection with the appended drawing in which,

FIG. 1 is a vertical cross-sectional view, with parts broken away, of a fluorescent lamp constructed in accord with the present invention,

FIG. 2 is a perspective view of a spring mounting means suitable for use in the apparatus of FIG. 1, and

FIG. 3 is a schematic circuit drawing of a radio frequency oscillator suitable for inclusion within the device of FIG. 1.

FIG. 1 illustrates, in vertical cross section with parts broken away, a typical structure of a low power electrodeless fluorescent lamp in accord with the present invention, suitable for substitution in place of a conventional household incandescent lamp. In FIG. 1, lamp apparatus 10 includes a base assembly 11 and a lamp envelope assembly 12. Base assembly 11 includes, typically, a screw type base 13 containing a pair of electrical contact members 14 and 15, which are insulated from one another and adapted to mate with the contact members of a conventional incandescent lamp socket. A solidstate power-generating means case 16is affixed to base 13 and contains a transistor oscillator, for example, for transforming the conventional household voltage of approximately 110 volts RMS into a suitable radio frequency voltage, which may be coupled to a ferrite core for transformation to an alternating voltage of proper value to operate the fluorescent lamp envelope assembly 12 for the production of high-efiiciency fluorescent light. Although such solid-state oscillators are well known to the art, one such oscillator which may be utilized in accord with the present invention is that disclosed in my copending application, Ser. No. 653,749, filed July 17, 1967, and assigned to the assignee of the present invention, the entire disclosure of which is incorporated herein by reference thereto. This oscillator is reproduced as FIG. 3 herein. Although that oscillator was designed to operate at a frequency of approximately kc., the preferable operating frequency of the oscillator in accord with the present invention is approximately 50 kc. Changes in the capacitive elements of that circuit to accomplish such frequency are obvious to one skilled in the art in order to adapt such oscillator for use in accord with the present invention. Accordingly, for the sake of clarity and brevity, such minor modifications will not be discussed herein.

Typically, the oscillator means case may include a metallic or suitable hard plastic container such as a cylindrical cup-shaped member 17 having an apertured cap member 18, adapted to screw or otherwise fit into, and

close, cup member 17. Cap 18 is suitably adapted to receive a rod-shaped ferrite core 19 which may, for example, be threaded into flange member 20 or cap 18 to secure core member 19 in fixed relation thereto. Alternatively, core member 19 may be otherwise afiixed to cap 18 or any portion of container 17, as for example, by a pressed fit. Flange 20 includes an upwardly-depending collar 21, which defines a shoulder 22 over which suitable mounting means may be placed to leave a spacing 22 about core member 19.

A removeable cap member 23 which may, for example, comprise a suitable hard plastic, is adapted to be permanently affixed in removeable relationship to the upper end of core rod 19, as for example, by screw threads 24, Alternatively, a bayonet-type socket or other means for rigidly and removeably afiixing member 23 to core 19 may be utilized.

A primary winding 25, having a relatively few number of turns, as for example, 3 to complete turns, constitutes a primary winding for the ferrite transformer including rod core 19, and is connected to the solid-state power generation means within case 16 by means of lead wires 26 and 27. A secondary starting winding 28, which may comprise a relatively large number of turns, as for example to 100, is wrapped about rod-shaped core 19 and is terminated in a pair of outwardly-depending, electrically-insulated tabs 29 and 30. Fluorescent lamp envelope 12 fits in rigid, but removeable, relationship concentrically about core member .19 and is held in place by end member 23. In order that envelope member 12 be rigidly affixed, it is held in rigid radial position by a slotted cylindrical spring member 31 which is in slight compressive stress and outwardly presses against envelope member 12 to maintain it in correct radial alignment.

Spring sleeve 31, which is illustrated in perspective in FIG. 2, fits about upwardly-depending collar 22 of cap member 18 of power supply case 16 and is held between collar 22 and downwardly-depending collar 32 of upper cap member 23. In positioning sleeve spring member 31 over the core member, the sleeve is positioned so that insulated tabs 29' and of starting secondary winding 28 protrude through the slot 33 in spring member 31. To assemble the lamp assembly, cylindrical slotted spring member 31 is placed over shoulder 22 with tabs 29 and 30 passing through slot 33. End cap member 23 is then screwed or otherwise fixedly mounted upon and into ferrite rod 19, as for example, by threads 24, so that collar 32 impinges between spring member 31 and core member 19, thus producing an outwardlydepending spring force against the envelope assembly 12, which is held firmly in position by the downwardlydepending surface of end member 23.

Fluorescent light-emitting envelope member 12 includes a torroidal or annular shaped, hollow evacuable envelope 40, having an outward surface 41 which simulates, together with the curvature of end cap 23, the conventional geometry of an incandescent lamp. Envelope also has an inner cylindrical wall 42, adapted to mate with spring member 31, and upper and lower ends 43 and 44, respectively, which are flat, so as to mate with the power supply container 16 and the end member 23.

Envelope 40 is filled with an inert starting gas, which may typically be argon at a pressure of approximately 2 to 4 torr, and sufficient mercury to create a partial pressure thereof of approximately 5 to 10 microns. For an operating temperature of 40 0., this may conveniently be 40 to milligrams of mercury, thus insuring the proper operating pressure and suitable excess mercury to maintain this pressure in the event of vapor cleanup. The inner sprface of envelope 12 is coated with a fluorescent, light-emitting phosphor which is responsive to the radiation of the mercury, when ionized, to emit light within the visible spectrum. Such phosphors are well known to the art and generally are either calcium halophosphates or calcium fluoro-phosphates, the many variations of which are well known to the art.

One of the most important of the criteria in constructing lights in accord with the present invention is that the ferrite rod be chosen of a material which, at the operating frequency, has a relatively low loss so as to transmit a maximum proportion of power input thereto to the fluorescent envelope for excitation of the mercury therein and the subsequent radiative excitation of the phosphor. One suitable ferrite is known as 3B7 and is obtainable from Ferroxcube Corporation of Saugerties, N.Y. This ferrite, when operated at a frequency of 50 kilocycles per second and at a 1000 gauss magnetic flux density, operates to have a bulk power loss of only approximately 15 milliwatts per cubic centimeter. This makes it possible for a typical lamp which may, for example, have a 30 watt characteristic, utilize a ferrite rod of approximately 0.75 inch in diameter and three and one half inches in length, to dissipate only approximately several watts in heating losses within the ferrite.

Although this particular ferrite has been set forth herein by way of example, the choice of an ideal ferrite for a particular lamp and for a particular operative environment is a matter of choice to those skilled in the art, and many other ferrites may be chosen by a study of their characteristic loss and dissipation characteristics.

One lamp in accord with the present invention operates at a 30 watt rating and, as noted hereinbefore, utilizes a 3.5 inch long, 0.75 inch diameter ferrite rod. The transistor oscillator utilizes 200' volt transistors which may be Delco DTS 423 or 431 or Motorola M] 413 or 423 and provides an output of 50 kHz. alternating current to a five turn primary at 50 volts and 0.6 ampere. An annular, light-emissive envelope has a longitudinal dimension of three inches and an annular inverted, truncated tear-shaped configuration with a maximum O.D. of three inches and an inner cylindrical aperture having an ID. of one inch. This envelope contains 50 mg. of mercury and 5 torr of argon and the inner surface thereof is coated with a calcium fiuorophosphate phosphor and constitutes a single turn secondary. When connected to a 110 volt supply line, a secondary voltage of approximately lO volts at approximately three amperes is induced therein with a total power loss of only approximately three watts through the ferrite core and produces fluorescent light having a lumen efficiency of approximately 40 lumens per watt when operated at an operating temperature of 40 C.

Although the foregoing example of one lamp constructed in accord with the present invention illustrates typical values of parameters which may be utilized in construction of one lamp in accord with the present invention, it is apparent that by appropriate modification of these parameters, lamps having various input powers and lumen outputs, may be constructed utilizing the general teachings herein.

In accord with the present invention, instant starting is obtained in lamps of the invention by the application of a capacitively coupled high voltage of the order of 1000 volts to the inner wall of envelope 12. This is accomplished by secondary winding 28, which may conveniently have turns terminating in tabs 29 and 30 which pass through the slot 33 in slotted spring 31 to impinge upon the inner wall 32 of envelope 40. Tabs 29 and 30 capacitively couple the high starting voltage into envelope 41 to cause instant ionization of the argon starting gas and the subsequent ionization and breakdown of the mercury contained therein.

In further accord with the present invention, loss by absorption of radiation directed inwardly from the annular lamp member 12 is prevented by causing spring member 31 to be constructed of a highly-reflective substance, as for example, aluminum or any high-polished metal or a metal with a silver plating.

In further accord with the present invention, the base member 11 of the present invention is designed to be a permanent member which need not be replaced. Although the life of conventional fluorescent lamps is very long as compared with incandescent lamps, it is not necessary to dispose of the lamp of the present invention, even upon failure of the fluorescent envelope. Normally this failure will be very long in occurring because, in addition to the well-known, long lifetime of fluorescent lamps, this lamp operates without electrodes under the principles generically disclosed and claimed in my aforementioned copending application, so that electrode deterioration, one of the prime causes of fluorescent lamp failure, is completely absent.

If, however, the light transmissive wall 40 should become fractured or if the phosphor should eventually become burned out, it is only necessary to unscrew end cap 23, remove light-emitting envelope member 12 and replace it, returning end cap member 23 to place and essentially a new lamp is ready for return to operation.

From the foregoing it is apparent that I have described a new type of fluorescent lamp suitable for utilization in direct substitution for conventional household incandescent lamps having any conventional base configuration, as for example, a screw-type base. These lamps are of greater efliciency than incandescent lamps and have a much greater lifetime and may be renewed by the substitution of a new light-emissive element should the original light-emissive element become damaged or burned out. This is accomplished by utilizing a solid-state oscillator to generate a radio frequency voltage and a ferrite core for transforming this voltage into a suitable operating voltage to excite the fluorescent lamp to light emission.

While the invention has been described in detail herein in accord with certain preferred embodiments thereof, many modifications and changes therein may be effected by those skilled in the art. Accordingly, it is intended, by the appended claims, to cover all such modifications and changes as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. Fluorescent lamp apparatus comprising:

(a) a first integral base member including:

(a a contact type base member adapted to fit into an incandescent lamp socket,

(a a power supply member fastened to said base and including a solid state radio frequency oscillator,

(a a rod-like ferrite core member attached to said base and power supply member, and

(a.;) means coupling the output of said radio frequency oscillator to said ferrite core;

(b) a second removable bulb member including:

(b an annular shaped evacuable light-trans-.

missive envelope adapted to fit over said rodlike ferrite core member,

(b an ionizable medium within said envelope adapted to sustain an electric discharge due to the electric field induced therein by said ferrite core when energized, and to emit a predetermined wavelength radiation when sustaining said discharge, and

(b a luminescent phosphor on the interior of said envelope wall adapted to emit visible radiation when excited by said first wavelength radiation; and

(c) means for securely but removably fastening said bulb member in place with said integral base member.

2. The apparatus of claim 1 wherein said means for coupling said radio frequency oscillator to said ferrite core member is a primary winding of approximately 2 to 10 turns suflicient to supply from 10 to 100 watts of input power thereto.

3. The apparatus of claim 1 wherein said ferrite core member has a characteristic of dissipating less than milliwatts of power per cubic centimeter thereof at a ,frequency of approximately kHz. and 1000 gauss magnetic flux density.

4. The apparatus of claim 1 wherein a starter secondary winding is wound around said ferrite core and the terminals thereof are capacitively coupled to said lamp envelope.

5. The apparatus of claim 4 wherein said starter winding generates a voltage output of at least 1000 volts RMS.

6. The lamp of claim 1 wherein said means for holding said lamp bulb on said base assembly includes a slotted spring loaded reflective cylindrical member be tween said ferrite rod and said envelope wall.

7. The apparatus of claim 6 wherein said holding means further includes a locking member fastened to said ferrite core member and having a diameter sufliciently large as to hold said bulb member in place.

8. The apparatus of claim 3 wherein said radio frequency value and said ferrite core characteristic, together with the chosen member of primary winding turns are suflicient to induce a secondary voltage in the ionizable medium within said bulb of approximately 5 to 20' volts RMS.

9. The apparatus of claim 8 wherein said induced secondary voltage is approximately 10 volts RMS at approximately 3 amperes.

References Cited UNITED STATES PATENTS 2,030,957 2/1936 Bethenod et a1. 3l5--248 2,149,414 3/1939 Bethenod 315-248 3,109,960 11/1963 Bell et a1 315248 3,196,312 7/ 1965 Marrison 3l5-348 X 3,227,923 1/ 1966 Marrison 315248 1,963,963 6/1934 Barclay 315-57 X JAMES W. LAWRENCE, Primary Examiner C. R. CAMPBELL, Assistant Examiner US. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT N0. 3 521,120

DATED July 21, 1970 INVENTOR(S) John M. Anderson It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In column 6, claim 3, line 20, insert --50-- before "kHz."

Signed and Scaled this Fourteenth D3) Of September 1976 [SEAL] A nest:

RUTH C. MASON C. MARSHALL DANN .-tl!eslr'ng Officer (mmm'ssirmor uj'Parenls and Trademarks 

